Internet Engineering Task Force (IETF) J. Chu
Request for Comments: 6928 N. Dukkipati
Category: Experimental Y. Cheng
ISSN: 2070-1721 M. Mathis
Google, Inc.
April 2013
Increasing TCP's Initial Window
Abstract
This document proposes an experiment to increase the permitted TCP
initial window (IW) from between 2 and 4 segments, as specified in
RFC 3390, to 10 segments with a fallback to the existing
recommendation when performance issues are detected. It discusses
the motivation behind the increase, the advantages and disadvantages
of the higher initial window, and presents results from several
large-scale experiments showing that the higher initial window
improves the overall performance of many web services without
resulting in a congestion collapse. The document closes with a
discussion of usage and deployment for further experimental purposes
recommended by the IETF TCP Maintenance and Minor Extensions (TCPM)
working group.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6928.
Chu, et al. Experimental [Page 1]RFC 6928 Increasing TCP's Initial Window April 2013Copyright Notice
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Table of Contents
1. Introduction ....................................................3
1.1. Terminology ................................................4
2. TCP Modification ................................................4
3. Implementation Issues ...........................................5
4. Background ......................................................6
5. Advantages of Larger Initial Windows ............................7
5.1. Reducing Latency ...........................................7
5.2. Keeping Up with the Growth of Web Object Size ..............8
5.3. Recovering Faster from Loss on Under-Utilized or
Wireless Links .............................................8
6. Disadvantages of Larger Initial Windows for the Individual ......9
7. Disadvantages of Larger Initial Windows for the Network ........10
8. Mitigation of Negative Impact ..................................11
9. Interactions with the Retransmission Timer .....................11
10. Experimental Results From Large-Scale Cluster Tests ...........11
10.1. The Benefits .............................................11
10.2. The Cost .................................................12
11. Other Studies .................................................13
12. Usage and Deployment Recommendations ..........................14
13. Related Proposals .............................................15
14. Security Considerations .......................................16
15. Conclusion ....................................................16
16. Acknowledgments ...............................................16
17. References ....................................................16
17.1. Normative References .....................................16
17.2. Informative References ...................................17
Appendix A. List of Concerns and Corresponding Test Results .......21